Ambient Air Passive Sampler for NO-NO2, NOx, SO2, O3, NH3. The Ogawa Sampler is ideal for low-cost air monitoring programs, personal, outdoors and indoors. The only known method of passive simultaneous monitoring of NO & NO2. The Ogawa Sampler is reusable countless times. Only the pre-coated filter pad is expendable. The same sampler is used for all above shown gases.